There are many in the data center industry that remain skeptical that containers or modular data centers will ever see wide adoption. This sentiment is driven, in part, by the lack of publicly-identified end users, beyond Microsoft and Google.

But that's starting to change. One of the nation's major telecom companies is now using container data centers to provide managed hosting services to its customers. That news comes from Active Power, which described the project in a press release announcing nearly $5 million in new orders for its PowerHouse, a container housing flywheel UPS and generator systems.

One of the orders will provide four containers housing power support systems for a container data center. "Owned by a leading telecommunication provider, the server container will offer managed hosting services for a variety of organizations," the company said.

Why are there so few announcements of container deployments? One reason can be seen in the other project mentioned in Active Power's announcement, in which a PowerHouse system will be deployed for a branch of the U.S. military. Several containers vendors have reported sales to military and government customers, and the General Services Administration is now preparing a buying guide for data center containers for federal agencies.

"The preassembled and pretested datacenter and its associated power and cooling infrastructure continues to become more mainstream, particularly among large IT and server OEM companies," said Martin Olsen, vice president, Global Channels and Business Development, Active Power. "It all comes down to a much lower total cost of ownership with this modular approach versus the component by component build out of a monolithic datacenter."